What happens when you resend an email?

Resending attempts to send essentially the same message again, often from the Sent folder. Some clients keep the original body and subject but create a fresh Message ID, while others keep more of the original structure.

From a filtering point of view, a resent copy is still a new message that must pass SPF, DKIM, and DMARC checks again. If the content is identical and sent repeatedly to many recipients, it can start to look like automated or bulk traffic. Resend is best used as a careful correction, not as a bulk sending shortcut.